where, \(L(r)\)  shows the outward flow of thermal energy, i.e. luminosity, and \(\epsilon \) 
is the rate of energy produced per unit mass. Outside the core this value becomes equal to the solar luminosity (\(L_{\odot }\) ). The solution for these equations are given with the two boundary conditions, i.e, \(M=0\) , \(\frac{dT}{dr}=0\)  at the center (\(r=0\) ), and \(M=M_{\odot }=1.989\times 10^{30}\)  kg, \(L=L_{\odot }=3.846\times 10^{26}\)  Watt, at the solar surface (\(r=R_{\odot }\) ). The solution gives an estimation about the size of the core (0.25 \(R_{\odot }\) ) and the base of the convection zone, which extends to 0.7 \(R_{\odot }\) . At this height of \(\approx \)  0.7 \(R_{\odot }\)  (\(T=10^6\)  K) convection instability occurs [1]}. This onset of instability is explained in Figure REF . Let us consider vertically stratified plasma with pressure (\(p(r)\) ), density (\(\rho (r)\) ), temperature (\(T(r)\) ) is in hydrostatic equilibrium and an elementary plasma blob moves in upward direction. The blob is supposed to be in equilibrium with the surrounding, such that it maintained the horizontal pressure ([2]}; [1]} [4]}). It rises up with a buoyancy force under the condition:
<FIGURE>\(\delta \rho _i < \delta \rho \) 
